CRISPLD2 Attenuates Intervertebral Disc Degeneration by Suppressing Oxidative Stress-Induced Ferroptosis through the miR-548I-IL17A Axis.

Intervertebral disc degeneration (IVDD) is a major cause of chronic low back pain, yet its molecular mechanisms remain unclear. We identified CRISPLD2 (cysteine-rich secretory protein LCCL domain-containing 2) as a critical regulator of nucleus pulposus cells (NPCs) homeostasis during IVDD. Single-cell transcriptomic analysis (scRNA-seq) revealed degenerative NPCs subsets enriched in iron metabolism and lipid peroxidation. CRISPLD2 knockdown in NPCs led to disrupted redox balance, elevated lipid peroxides, and excessive iron accumulation, promoting oxidative stress-induced ferroptosis and disc degeneration. Mechanistically, we identified a CRISPLD2-miR-548I-IL17A axis that governs ferroptotic cell death in IVDD, where CRISPLD2 deficiency was associated with reduced miR-548I expression, accompanied by subsequent upregulation of IL17A, thereby amplifying inflammatory and oxidative stress responses. In vivo, CRISPLD2 knockdown induced spontaneous IVDD and increased pain sensitivity, while restoration of CRISPLD2 or inhibition of IL17A alleviated ferroptosis and improved NPCs survival. Adeno-associated virus (AAV)-mediated overexpression of CRISPLD2 successfully alleviated IVDD in lumbar spine instability and needle-puncture models, reducing oxidative stress-induced ferroptosis and restoring disc integrity. These findings highlight the critical role of CRISPLD2 in regulating oxidative stress-induced ferroptosis in IVDD and suggest that targeting the CRISPLD2-miR-548I-IL17A axis may provide a novel therapeutic strategy for preventing disc degeneration and alleviating discogenic pain.